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Step 3 Sample Test Answers + Explanations 2026
USMLE STEP 3 Free 137 Explanations
Updated June 2026


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Updated as of June 2026
Here are the detailed explanations of the new Free 137 NBME STEP 3 Sample Test Questions so you don’t waste your time trying to find the correct answers and explanations. We had our expert USMLE tutors who scored 260+ on their exams refine these answers and explanations for you so you can spend your valuable time learning!
You can download the Free 137 STEP 3 Sample Test Questions on the USMLE website here. The order of answers and explanations here is based on the online NBME platform (not the pdf) as of June 2026.
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Table of Contents
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Block 1
Question 1:
The correct answer is E. This 55-year-old man has symptoms and physical findings suggestive of aortic regurgitation (AR). The patient’s bounding pulses, widened pulse pressure, displaced point of maximal impulse (PMI), and a diastolic decrescendo murmur are classic for AR. Transthoracic echocardiography (TTE) is the best initial test to confirm the diagnosis, assess the severity, and evaluate for underlying causes.
Aortic Regurgitation (AR):
Pathophysiology: Backflow of blood into the left ventricle during diastole, leading to left ventricular volume overload and eventual dilation.
Clinical Features: Fatigue, exertional dyspnea, chest discomfort (due to increased myocardial oxygen demand). Bounding pulses, wide pulse pressure, displaced PMI, and diastolic murmur.
Diagnosis: TTE is the gold standard for diagnosing AR, assessing valve anatomy, and determining the degree of regurgitation.
Management:
Mild AR: Medical management (e.g., afterload reduction with ACE inhibitors or calcium channel blockers).
Severe AR: Surgery if symptomatic or evidence of left ventricular dysfunction.
Incorrect answers:
A. Arterial brachial index of the lower extremity: Used to assess peripheral arterial disease, not relevant for AR.
B. Coronary angiography: Indicated for suspected coronary artery disease, which is not evident here.
C. Pulmonary function testing: Not related to cardiac symptoms or findings.
D. Renal ultrasonography: No indication of renal pathology or hypertension secondary to renal artery stenosis.
Question 2:
The correct answer is E. This 16-year-old patient exhibits academic decline and cannabis use. The physician must balance maintaining confidentiality with ensuring the patient receives appropriate support. A non-judgmental approach that focuses on the effects of cannabis use on functioning encourages trust and opens the door for collaborative problem-solving. Offering to facilitate communication with the mother ensures that the patient receives family support without breaching confidentiality. Adolescents often minimize the impact of substance use. Maintaining the adolescent’s confidentiality is essential for maintaining a trusting physician-patient relationship.
Incorrect answers:
A. “I am worried about your cannabis use…”: This approach is passive and delays intervention, missing an opportunity to engage the patient constructively.
B. “I can give you a telephone number for enrollment…”: Providing a referral without addressing the patient’s concerns minimizes the physician’s role in the initial conversation.
C. “Cannabis is bad for your brain…”: Lecturing the patient risks alienating them and does not foster a collaborative approach.
D. “Because you are not actually using this…”: Dismissing the problem undermines the seriousness of the patient’s substance use and its impact on functioning.
Question 3:
The correct answer is C. This patient with severe COPD and a do-not-resuscitate (DNR) order is requesting removal of noninvasive positive pressure ventilation (NIPPV). The appropriate next step is to clarify her goals of care and confirm that her wishes align with her documented advance directive. Since the directive appears unclear, engaging her in a detailed discussion ensures she understands the implications of her decision.
When a patient’s advance directive is unclear or does not fully address their current situation, it is essential to have a direct and empathetic discussion to clarify their goals of care and document their updated preferences. This ensures that medical interventions align with the patient’s values and wishes.
Incorrect answers:
A. This approach does not adequately address her current concerns or explore her preferences.
B. The patient is competent and can make decisions herself, so involving the family is unnecessary unless she requests it.
D. This contradicts the patient’s initial decision to decline intubation.
E. There is no evidence of impaired decision-making capacity, so this step is not warranted.
Question 4:
The correct answer is C. The study compared emergency portacaval shunt (EPCS) with endoscopic sclerotherapy (EST) in patients with cirrhosis and acute bleeding esophageal varices. One of the significant findings was a reduction in recurrent portal-systemic encephalopathy (PSE) with EPCS (15%) compared to EST (35%). Based on the abstract, the number needed to treat (NNT) to prevent one case of recurrent PSE is calculated using the relative risk reduction (RRR):
RRR = (35% – 15%) / 35% = 20% / 35% ≈ 0.57.
NNT = 1 / Absolute Risk Reduction (ARR) = 1 / (35% – 15%) = 1 / 0.20 = 5.
Therefore, approximately 5 patients must be treated with EPCS instead of EST to prevent one case of recurrent PSE.
Question 5:
The correct answer is B. The study’s generalizability is limited by the fact that emergency portacaval shunt (EPCS) is a technically demanding procedure requiring specialized expertise and facilities, making it accessible only at tertiary or specialty centers. This limits its widespread application, particularly in smaller or rural hospitals.
Factors limiting generalizability:
EPCS requires highly skilled surgeons and advanced equipment.
Patients in community settings may not have timely access to this intervention.
The study was conducted at a single tertiary care center, further restricting its applicability to other settings.
Incorrect answers:
A. The allocation was concealed: This ensures validity, not generalizability.
C. The follow-up period was too short: The study had a follow-up of up to 17 years, which is sufficient.
D. The patients were not blinded: Blinding may be difficult in surgical trials but does not impact generalizability.
E. Unmeasured confounders were not controlled by the study design: The study design appears rigorous, with randomization and concealed allocation.
Question 6:
The correct answer is B. The table in the abstract shows that the mean number of hospital readmissions for variceal bleeding requiring transfusion was significantly lower in patients undergoing EPCS (0.4) compared to those receiving EST (6.8). This highlights the superior efficacy of EPCS in controlling bleeding and preventing hospitalizations.
Key findings supporting the answer:
EPCS patients had significantly fewer readmissions compared to EST patients.
The difference in efficacy is statistically significant (P < .001).
Incorrect answers:
A. This is not supported by the abstract; survival differences are clearly significant.
C. EPCS improves survival, especially for patients in Child-Pugh classes A and B.
D. The study describes appropriate randomization and concealed allocation, ensuring validity.
Question 7:
The correct answer is B. This 4-year-old boy presents with weight loss, fatigue, and hyponatremia with normal potassium levels. His physical exam and laboratory findings suggest secondary adrenal insufficiency due to chronic suppression of the hypothalamic-pituitary-adrenal (HPA) axis, likely caused by long-term glucocorticoid therapy for asthma. Prolonged use of corticosteroids suppresses the release of corticotropin-releasing hormone (CRH) from the hypothalamus and ACTH from the pituitary gland, leading to adrenal atrophy and insufficient endogenous cortisol production.
Cortisol plays a critical role in maintaining vascular tone, blood glucose levels, and electrolyte balance. In secondary adrenal insufficiency, the lack of ACTH leads to low cortisol production, but aldosterone secretion (regulated by the renin-angiotensin-aldosterone system) remains intact. This explains the hyponatremia (caused by water retention due to cortisol deficiency) without hyperkalemia, distinguishing it from primary adrenal insufficiency (e.g., Addison disease). Management involves gradual tapering of corticosteroids to allow recovery of the HPA axis and, in acute situations, replacement of hydrocortisone or other glucocorticoids.
Incorrect answers:
A. Decreased activity of 21-hydroxylase enzyme: Seen in congenital adrenal hyperplasia, characterized by hyperkalemia, hyponatremia, and virilization in severe cases, which are absent here.
C. Decreased production of antidiuretic hormone (ADH): Causes diabetes insipidus with hypernatremia and dilute urine, not hyponatremia.
D. Increased aldosterone production: Leads to primary hyperaldosteronism (e.g., Conn syndrome), causing hypokalemia and hypertension, not the findings seen in this patient.
E. Increased insulin production: Associated with hypoglycemia, which is not relevant to this case.
Question 8:
The correct answer is E. This 64-year-old woman presents with acute shortness of breath, tachycardia, and hypoxemia. She has a history of chronic obstructive pulmonary disease (COPD) and recently underwent inguinal hernia repair, which places her at increased risk for venous thromboembolism (VTE) due to prolonged immobility and the hypercoagulable state associated with recent surgery. Despite clear lung fields and no evidence of pneumonia or heart failure on imaging, her elevated D-dimer suggests a thrombotic process, most consistent with a pulmonary embolism (PE).
Pulmonary embolism occurs when a thrombus, usually originating from the deep veins of the legs, dislodges and embolizes to the pulmonary arteries, causing ventilation-perfusion mismatch and impaired oxygenation. Classic symptoms include acute onset dyspnea, pleuritic chest pain, and tachycardia. Risk factors include surgery, immobility, cancer, and hypercoagulable states. While diagnostic imaging (e.g., CT pulmonary angiography) is often required for confirmation, an elevated D-dimer supports the presence of a thrombotic process. Prompt anticoagulation is the cornerstone of management, aiming to reduce clot propagation and prevent further embolization.
Incorrect answers:
A. COPD exacerbation: While COPD exacerbations can cause dyspnea, they are usually accompanied by wheezing, increased sputum production, or infectious symptoms, none of which are present here. Normal lung sounds also argue against this diagnosis.
B. Heart failure: The absence of bilateral rales, peripheral edema, or significant elevation in BNP makes heart failure unlikely. The patient’s BNP is within normal limits for her age.
C. Pneumonia: Pneumonia typically presents with fever, productive cough, and radiographic consolidation, none of which are evident in this patient.
D. Pneumothorax: Pneumothorax causes acute dyspnea with decreased or absent breath sounds on the affected side. This patient has clear lung fields bilaterally, ruling out this diagnosis.
Question 9:
The correct answer is C. The question presents two tests, A and B, with their respective receiver operating characteristic (ROC) curves. Test A’s curve lies above Test B’s curve in the low false-positive rate range (left side of the graph), indicating that Test A is more accurate in this range. Accuracy is determined by the area under the curve (AUC), and in this specific segment, Test A demonstrates higher sensitivity for lower false-positive rates compared to Test B.
ROC curves plot sensitivity (true positive rate) against 1-specificity (false positive rate) and help compare diagnostic tests. The closer the curve is to the upper-left corner, the more accurate the test. AUC provides a single measure of overall test performance; a higher AUC corresponds to better test accuracy. When assessing tests for different clinical scenarios, it is crucial to consider the acceptable trade-off between sensitivity and specificity, depending on the condition being diagnosed.
Question 10:
The correct answer is E. This 19-year-old college student presents with fever, chills, headache, nonproductive cough, macular rash with petechiae, and generalized weakness. On physical exam, erythematous macular lesions with petechiae are observed on the palms, soles, legs, and thighs. Laboratory findings include a mildly elevated white blood cell count with a left shift, thrombocytopenia, and cerebrospinal fluid (CSF) with a high opening pressure, slightly elevated protein, and normal glucose. These findings, combined with his geographic location (Western North Carolina) and occupational exposure (greenskeeper), are highly suggestive of Rocky Mountain spotted fever (RMSF) caused by Rickettsia rickettsii.
RMSF is a tick-borne illness transmitted by the Dermacentor species of ticks. It is commonly found in the southeastern and south-central United States. The hallmark features of RMSF include fever, headache, myalgia, and a characteristic rash that typically starts on the wrists and ankles and spreads centrally, often involving the palms and soles. The infection leads to vascular endothelial damage, resulting in increased vascular permeability, hypovolemia, and organ dysfunction. Diagnosis is clinical, as early recognition and treatment are critical to prevent severe complications, such as encephalitis, pulmonary edema, and disseminated intravascular coagulation.
Question 11:
The correct answer is D. This 19-year-old pregnant woman’s history of continued smoking during pregnancy significantly increases the risk of sudden infant death syndrome (SIDS) for her infant. Maternal smoking is the most critical modifiable risk factor for SIDS.
SIDS and maternal smoking: Smoking during pregnancy exposes the fetus to nicotine and other harmful chemicals that can impair autonomic regulation, increasing SIDS risk. Second-hand smoke after birth compounds the risk. Risk reduction strategies include smoking cessation, safe sleep practices (e.g., supine sleeping position), and breastfeeding.
Other Risk Factors for SIDS:
- Maternal/antenatal:
o Substance use: Cigarettes, alcohol, recreational drugs.
o Maternal age <20.
o Inconsistent prenatal care.
- Infant-related:
o Prematurity or low birth weight.
o Unsafe sleep environment: Prone/side sleeping, soft bedding, or bed-sharing.
o Smoke exposure (maternal or secondhand).
Incorrect answers:
A. Employment status: Unemployment is associated with socioeconomic challenges but is not a direct risk factor for SIDS.
B. History of cocaine use: The patient’s urine screening was negative, and cocaine use is not a primary risk factor for SIDS.
C. Lack of breastfeeding: While breastfeeding reduces SIDS risk, it is not as significant as maternal smoking.
Question 12:
The correct answer is B. his 75-year-old man presents with fever, pleuritic chest pain, cough producing rust-colored sputum, and consolidation in the left lower lobe, suggestive of left-sided lobar pneumonia. His symptoms worsen when he is lying on his left side, likely due to the effects of gravity on the consolidated lung. In this position, blood flow is diverted to the left lung, which has impaired oxygenation due to the consolidation, worsening the ventilation-perfusion mismatch and increasing the A-a gradient, leading to hypoxemia. When the patient is rolled to his right side, gravity helps redistribute the blood flow to the right lung, which is likely less affected by the pneumonia and is better aerated. Positional changes that favor the unaffected lung (right side in this case) can reduce the mismatch in ventilation and perfusion caused by the consolidated lung.
Incorrect answers:
A. Pulmonary embolism typically presents with sudden onset dyspnea, tachypnea, hypoxemia, and pleuritic chest pain. However, the findings of consolidation on chest x-ray, rust-colored sputum, and the gradual onset of symptoms are more indicative of pneumonia rather than a pulmonary embolism.
C. Left ventricular filling abnormalities, such as those seen in restrictive cardiomyopathy or tamponade, can cause positional symptoms, but they would not explain the focal lung findings (consolidation) or improvement with positional changes specific to pneumonia.
D. While a large pleural effusion or consolidation could restrict diaphragmatic motion, it would cause more gradual changes in breathing and wouldn’t result in the rapid improvement in symptoms seen here.
E. While pleural fluid shifts with position, the fluid doesn’t increase; it redistributes. The immediate symptom improvement suggests that the relief is due to a redistribution of blood flow, not the increase of pleural effusion. Also, the chest x-ray does not show any evidence of pleural effusion.
Question 13:
The correct answer is C. This 12-year-old girl with a seizure disorder is requesting a dose of carbamazepine and a prescription refill. However, since the patient is a minor and her aunt is not a legal guardian, the physician is obligated to contact the mother to obtain informed consent. Treatment without guardian consent is permissible only in emergency situations where the child’s life or health is at immediate risk, which is not the case here.
Key Considerations in Minors:
Informed Consent: Legal guardians (usually parents) must provide consent for non-emergent treatment in minors.
Emergencies: In life-threatening situations (e.g., status epilepticus), treatment can proceed without consent to protect the minor’s health.
Non-Emergent Situations: Physicians must attempt to contact the parent/guardian for consent, even if the child requests treatment.
Application in This Case: Since the patient is stable, the focus should be on obtaining consent before administering medication or writing a prescription. The mother’s consent ensures adherence to legal and ethical obligations.
Incorrect answers:
A. Administer the dose of carbamazepine and provide a prescription: This action requires parental consent in non-emergency situations.
B. Administer the dose of carbamazepine but do not provide a prescription: Both actions require guardian consent.
D. Do not contact the mother but request that the aunt sign a consent form: The aunt is not legally authorized to provide consent.
E. Provide a prescription, but do not administer the dose of carbamazepine: Writing a prescription also requires parental consent.
Question 14:
The correct answer is D. This patient presents with symptoms and physical findings consistent with osteoarthritis (OA), including joint pain, morning stiffness lasting less than 30 minutes, and bony enlargement. OA is characterized by the progressive loss of articular cartilage, leading to bone remodeling. X-ray findings commonly include joint space narrowing, subchondral sclerosis, osteophyte formation, and bony cysts.
OA is the most common joint disorder, especially in weight-bearing joints like the knees. Risk factors include age, obesity, prior joint injury, and mechanical stress. Radiologic findings reflect structural changes, and treatment involves weight loss, physical therapy, and pain management with NSAIDs or acetaminophen.
Incorrect answers:
A. Bone demineralization and erosions: These findings are characteristic of inflammatory conditions like rheumatoid arthritis, not OA.
B. Soft tissue swelling, sclerotic joint margins, and large cystic erosions: This suggests crystal-induced arthritis (e.g., gout), which does not match this patient’s chronic presentation.
C. Soft tissue swelling with no evidence of cartilage or bone destruction: This is typical of inflammatory arthritis in its early stages, not OA.
E. No abnormal findings: This is incorrect as OA typically has characteristic x-ray findings, including joint space narrowing and osteophytes.
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Question 15:
The correct answer is B. This 54-year-old woman presents with recurrent upper abdominal pain, nausea, and burning throat sensations, which have not improved despite recommended lifestyle modifications and medication adherence. She is preoccupied with her symptoms and requests an endoscopy, convinced that she has Barrett esophagus after researching online. Her anxiety and preoccupation with her health, as well as frustration with her symptoms, suggest a significant emotional component to her condition. The most appropriate next step is to explore her goals and expectations regarding treatment. This approach can help build rapport, address underlying concerns, and provide reassurance.
In patients with medically unexplained symptoms or excessive health-related anxiety, effective communication is key to management. It is important to validate the patient’s concerns, avoid unnecessary diagnostic tests, and provide reassurance without dismissing their symptoms. By understanding her goals, the physician can guide discussions toward realistic expectations, address misconceptions (e.g., overemphasis on Barrett esophagus), and encourage evidence-based treatment strategies.
Incorrect answers:
A. Ask the patient if she would like to see a specialist: Referring to a specialist without first addressing her emotional and cognitive concerns may reinforce her anxiety and focus on diagnostic procedures.
C. Ask the patient to further explain why she thinks she has Barrett esophagus: This may validate her fixation on a self-diagnosis rather than addressing her underlying anxiety and treatment expectations.
D. Discuss why the patient has not made the suggested changes to her diet and exercise: While lifestyle factors contribute to symptoms, this approach may appear dismissive or critical.
E. Encourage the patient to describe how she feels about having an unresolved medical condition: While important, this step is secondary to understanding her treatment goals.
Question 16:
The correct answer is C. This patient presents with generalized pruritus, recent use of oxycodone, and no significant physical findings apart from skin excoriations. Pruritus is a well-documented side effect of opioid therapy, including oxycodone. This side effect occurs due to opioid-induced histamine release from mast cells, leading to an itch sensation. The histamine release is independent of an allergic reaction and does not require discontinuation of the medication unless the pruritus is intolerable or unmanageable.
Incorrect answers:
A. Exacerbation of psoriasis: Psoriasis can cause pruritus, but it typically presents with characteristic erythematous, scaly plaques, which are not seen in this patient, and there’s no sign of psoriasis exacerbation.
B. Obstruction of the common bile duct: This typically causes jaundice and dark urine due to biliary obstruction, which isn’t consistent with this patient’s presentation or urinalysis findings.
D. Tamsulosin therapy: Tamsulosin, an alpha-blocker, can cause orthostatic hypotension or dizziness but is not commonly associated with pruritus.
E. Ureteral obstruction: While ureteral obstruction can lead to hematuria and pain, it would not typically cause generalized pruritus; the cause of pruritus is more likely related to the medication or another systemic issue.

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Question 17:
The correct answer is A. This patient presents with mild scleral icterus and a palpable epigastric mass, which are concerning for pancreatic malignancy, such as pancreatic adenocarcinoma. A CT scan of the abdomen is the most appropriate initial diagnostic test because it provides detailed imaging of the pancreas and surrounding structures to identify tumors, metastases, or biliary obstruction.
Pancreatic cancer often presents with nonspecific symptoms, such as anorexia, abdominal discomfort, or jaundice. A CT scan is the gold standard for initial evaluation, as it can identify mass lesions, ductal dilation, and vascular involvement. Further imaging, such as endoscopic ultrasound or MRI, may be used for staging or obtaining a tissue diagnosis.
Incorrect answers:
B. Determination of serum amylase and lipase concentrations: These are elevated in acute pancreatitis but are not helpful in diagnosing pancreatic cancer.
C. Endoscopic retrograde cholangiopancreatography: This is useful for biliary interventions but is invasive and not the first-line diagnostic test for a pancreatic mass.
D. HIDA scan: This is used to evaluate gallbladder function, which is not relevant in this case.
E. Upper gastrointestinal barium study: This is used for esophageal or gastric pathologies but does not provide imaging of the pancreas.
Question 18:
The correct answer is B. This patient presents with severe abdominal pain, fever, and physical findings consistent with acute mesenteric ischemia. Laboratory findings of metabolic acidosis and leukocytosis further support this diagnosis. The patient’s abdominal X-ray shows dilated loops of bowel, which is indicative of disruption of peristaltic activity secondary to ischemia. On surgical resection, histopathology in acute ischemic colitis typically demonstrates coagulative necrosis of the mucosa and submucosa due to hypoperfusion. In some cases, full-thickness necrosis may occur if ischemia is severe.
Incorrect answers:
A. Caseating granulomatous inflammation with serosal fibrous adhesions: This is seen in conditions like tuberculosis or Crohn disease, but the acute presentation, along with the patient’s risk factors, suggests ischemia rather than chronic granulomatous disease.
C. Neutrophilic infiltrates in the mucosa with venous congestion and edema: This is more typical of acute colitis or infection (eg, inflammatory bowel disease), not ischemia, where more severe necrosis occurs due to vascular compromise.
D. Patchy mucopurulent exudate with exploding glandular crypts: This describes a pattern seen in infectious colitis or inflammatory bowel disease but does not fit the acute ischemic injury seen in mesenteric ischemia.
E. Transmural chronic inflammation with ulcerations extending into submucosa: This is a hallmark of chronic inflammatory bowel diseases like Crohn disease, but this patient’s acute presentation and vascular issues point to ischemic infarction instead.

Block 2
Question 19:
The correct answer is B. Discrepancies in oxygen administration arise from unclear protocols. Standardizing orders ensures consistent care and reduces the risk of under- or over-administration.
Standardized protocols:
- Include clear titration guidelines.
- Prevent variability in physician and nurse practices.
- Enhance patient safety.
Implementation:
- Provide staff training on standardized protocols.
- Regular audits to ensure adherence.
Incorrect answers:
A. Conducting an in-service program: Useful but does not address systemic issues like unclear orders.
C. Encouraging nurses to refrain from adjusting therapy: Discourages autonomy without providing clear guidelines.
D. Requiring nurses to enter verbal orders: Increases administrative burden and risk of miscommunication.
E. Requiring calls for deviation: Inefficient and delays care.
Question 20:
The correct answer is C. The findings in the question describe a 29-year-old woman with HIV infection who is asymptomatic, has an undetectable viral load, and is considering pregnancy. The key consideration here is understanding the risk of perinatal HIV transmission. A maternal viral load is the strongest determinant of this risk. With effective antiretroviral therapy (ART), achieving an undetectable viral load minimizes the likelihood of transmission to less than 1%.
HIV can be transmitted from mother to child during pregnancy, delivery, or breastfeeding. The most critical factor influencing transmission is the maternal plasma HIV RNA level. With appropriate ART, the risk of transmission during delivery is exceedingly low. In addition, cesarean delivery may be recommended if the viral load is not adequately suppressed near term. Avoidance of breastfeeding is also crucial in preventing transmission.
Incorrect answers:
A. This statement is not directly related to perinatal transmission risk. Transmission is more closely associated with maternal viral load and interventions.
B. Intrapartum transmission does account for a substantial portion of cases, particularly without ART, but this statement doesn’t address the most critical determinant—maternal viral load.
D. While acute HIV infection during pregnancy is associated with higher transmission risk, this statement is less relevant in a patient with an undetectable viral load.
E. This is incorrect because cesarean delivery may reduce the risk of perinatal transmission in women with detectable viral loads.
Question 21:
The correct answer is F. This 24-year-old woman presents with recurrent episodes of irritability, insomnia, and mood swings that seem to occur in a cyclical pattern lasting 2–3 weeks. Her symptoms are likely related to her menstrual cycle, and timing of symptoms is crucial to differentiate between premenstrual dysphoric disorder (PMDD) and other mood disorders.
Key Features of PMDD:
Symptoms typically occur in the luteal phase (1–2 weeks before menses) and resolve with the onset of menstruation. Symptoms include mood changes, irritability, fatigue, insomnia, and physical symptoms (e.g., bloating, breast tenderness). Diagnosis relies on a clear temporal relationship with the menstrual cycle.
Next Steps:
Ask the patient to track her symptoms over 2–3 cycles to confirm the timing and relationship to menstruation. Management includes lifestyle modifications, SSRIs, and hormonal therapy (e.g., oral contraceptives).
Incorrect answers:
A. Carbohydrate intake: Not directly related to her mood or insomnia symptoms.
B. Coital frequency: Unrelated to her cyclic mood swings.
C. Frequency of physical activity: May impact overall well-being but is not the key history for this presentation.
D. History of psychological trauma: Relevant in other mood disorders but less likely with clear cyclic symptoms.
E. Stress level: Affects mood but does not explain the cyclic nature of her symptoms.
Question 22:
The correct answer is C. This 18-year-old woman seeks a prescription for Essepro XL, a medication indicated for attention-deficit/hyperactivity disorder (ADHD), to improve her academic performance and lose weight. However, the patient does not have a confirmed diagnosis of ADHD, and self-diagnosis or symptom exaggeration is common in patients seeking stimulants for academic or weight-loss purposes. Moreover, prescribing stimulant medication without a clear clinical indication risks misuse and potential side effects.
Stimulant medications like Essepro XL (focopheridate sodium) are controlled substances with abuse potential. They are indicated for ADHD and sometimes narcolepsy, but not for enhancing academic performance or weight loss. Off-label use can lead to dependency, cardiovascular side effects, and other complications. Physicians must carefully evaluate patients’ symptoms and consider non-stimulant therapies or behavioral interventions when the clinical picture is unclear.
Incorrect answers:
A. There is no evidence the patient is on other stimulants, making this incorrect.
B. The presence of a midsystolic click suggests mitral valve prolapse (MVP), which is typically benign and not a contraindication for stimulant use. However, it does warrant careful consideration when prescribing stimulants due to the potential for cardiovascular side effects, such as palpitations or arrhythmias. This is not the primary reason for not prescribing the medication in this case.
D. While this is a possibility, it is speculative and not the primary reason for avoiding prescribing the medication.
E. While true, the focus here is the lack of clinical indication for prescribing the medication, not weight loss efficacy.
Question 23:
The correct answer is F. The advertisement emphasizes that Essepro XL provides better sustained action compared to other medications in its class, including methylphenidate XL. Its improved “late afternoon performance” and long-lasting effects are noted as advantages, making its increased duration of action a key benefit. This longer effect may reduce the need for multiple daily doses, enhancing patient adherence and convenience.
Stimulant medications differ in pharmacokinetics, with some formulations offering prolonged action through controlled-release mechanisms. These medications are particularly useful for patients requiring extended symptom control, such as those managing ADHD symptoms throughout the school day and into the evening.
Incorrect answers:
A. Decreased likelihood of disrupted sleep patterns: Stimulants, including Essepro XL, commonly cause insomnia, and there is no indication that it reduces sleep disruption compared to others.
B. Decreased potential for dependency: Essepro XL, as a controlled substance, carries similar dependency risks to other stimulant medications.
C. Decreased rates of nausea and anorexia: Appetite suppression is a common side effect of stimulants, and no evidence suggests Essepro XL reduces this.
D. Increased academic performance: While stimulants improve focus in patients with ADHD, their academic benefits for non-ADHD individuals are unclear.
E. Increased availability of safety data: Essepro XL does not have more extensive safety data than other medications in its class.
Question 24:
The correct answer is D. This 63-year-old man presents with a history of transient monocular vision loss, likely due to amaurosis fugax, a transient ischemic event involving the retina. The most common etiology is retinal ischemia due to atherosclerotic emboli. These emboli usually originate from ipsilateral carotid artery. So, patients with risk factors, should be evaluated with an ultrasonography of the neck.
Amaurosis Fugax:
Pathophysiology: Typically caused by a transient embolus or hypoperfusion affecting the retinal circulation.
Presentation: Sudden, temporary monocular vision loss lasting seconds to minutes, with full resolution. Classic: Curtain descending over the visual field
Etiology: Most cases arise from embolic events (e.g., carotid artery atherosclerosis, atrial fibrillation). Other causes include retinal artery vasospasm or giant cell arteritis.
Carotid Ultrasonography: Non-invasive, highly sensitive and specific for detecting carotid artery stenosis.
Incorrect answers:
A. Fluorescein angiography of the right eye: Used to evaluate retinal vascular abnormalities, but not indicated here due to the transient nature of the event.
B. Measurement of intraocular pressures: Necessary for glaucoma, which is not suspected here.
C. Transesophageal echocardiography: Appropriate for suspected cardioembolic sources, but there is no evidence of embolism here.
E. No further evaluation is indicated: This is inappropriate, as amaurosis fugax often indicates underlying atherosclerotic disease or embolic risk that requires prompt evaluation to prevent future stroke or vision loss.
Question 25:
The correct answer is B. This 63-year-old woman developed acute kidney injury (AKI), as evidenced by rising creatinine, hyperkalemia, and oliguria. CKD, a known risk factor for AKI, predisposes patients to ischemic or nephrotoxic injury due to reduced renal reserve. The patient’s pre-existing stage 3 CKD likely contributed to her reduced ability to recover from acute stressors.
CKD is defined by a glomerular filtration rate (GFR) <60 mL/min/1.73 m² for more than 3 months. Chronic damage to nephrons reduces the kidney’s capacity to adapt to hemodynamic changes, making these patients vulnerable to AKI triggers such as volume depletion, nephrotoxins, or sepsis.
Incorrect answers:
A. Bladder catheterization: While this increases the risk of urinary tract infections, there is no evidence of infection here causing acute kidney injury.
C. Uncontrolled hypertension: Although this may contribute to chronic kidney damage, it is not the primary driver of AKI in this case.
D. Use of lisinopril: ACE inhibitors can cause AKI in volume-depleted patients, but there is no indication that lisinopril played a role here.
E. Volume depletion: The patient’s serum sodium and absence of orthostatic symptoms argue against significant volume depletion.
Question 26:
The correct answer is B. This 28-year-old man presents with dysuria and minimal urethral discharge. He is sexually active with one partner, but his symptoms are suggestive of a sexually transmitted infection (STI). The absence of significant discharge or systemic findings does not rule out gonococcal or chlamydial urethritis. A PCR test is highly sensitive and specific for diagnosing these infections, even in patients with mild or atypical presentations.
Gonococcal and chlamydial infections are the most common causes of urethritis in sexually active individuals. N. gonorrhoeae often causes purulent discharge, whereas C. trachomatis may result in a milder presentation. PCR-based testing is the gold standard due to its accuracy and ability to differentiate between pathogens, allowing for targeted treatment.
Incorrect answers:
A. Gram stain of urethral discharge before and after prostatic massage: Prostatic massage is not indicated here since the patient has urethritis symptoms, not prostatitis. Gram stain has limited sensitivity compared to PCR.
C. Urinalysis: While urinalysis can detect pyuria, it does not identify specific pathogens such as N. gonorrhoeae or C. trachomatis.
D. Urine culture and sensitivity: This is useful for bacterial UTIs, not STIs like gonorrhea or chlamydia.
E. No study, pending reevaluation of sexual history: This delays diagnosis and treatment, potentially worsening the condition and increasing the risk of transmission.

Question 27:
The correct answer is D. This 44-year-old woman reports an increase in the duration and amount of menstrual bleeding, lasting 10 days instead of her usual six. Her symptoms of heavy menstrual bleeding are accompanied by fatigue, which may indicate anemia. On examination, she has an enlarged uterus consistent with a myomatous (fibroid) uterus previously confirmed by ultrasound. While fibroids are a common cause of heavy menstrual bleeding, an endometrial biopsy is necessary to rule out endometrial hyperplasia or carcinoma, particularly in women over 40 with abnormal uterine bleeding (AUB).
Endometrial hyperplasia and carcinoma are often associated with unopposed estrogen exposure. Risk factors include obesity, polycystic ovarian syndrome (PCOS), and chronic anovulation, all of which lead to prolonged estrogen stimulation of the endometrium without opposing progesterone. Over time, this can cause endometrial thickening, atypia, and, eventually, malignancy. An endometrial biopsy is a minimally invasive and highly sensitive method to detect hyperplasia or malignancy. Early identification and management of endometrial hyperplasia can prevent progression to carcinoma, highlighting the importance of biopsy in this clinical scenario.
Incorrect answers:
A. Colposcopy: Used to evaluate abnormal cervical cytology or visible cervical lesions, not for investigating abnormal uterine bleeding (AUB).
B. Determination of FSH/LH concentrations: Appropriate for menopause evaluation but does not help identify structural or endometrial causes of AUB.
C. Serum prolactin determination: Used for amenorrhea or galactorrhea but does not address heavy menstrual bleeding.
E. Hysteroscopy: Useful for direct visualization of intrauterine pathology but is invasive and not the first-line diagnostic test for AUB.
Question 28:
The correct answer is A. This 2-month-old boy with conjugated hyperbilirubinemia, hypoplastic gallbladder on ultrasound, and elevated direct bilirubin is consistent with biliary atresia. The microscopic hallmark of biliary atresia is bile ductular proliferation, which results from obstruction of bile flow and progressive fibrosis.
Key Features of Biliary Atresia:
Progressive fibroinflammatory obliteration of the extrahepatic bile ducts, leading to biliary obstruction. Presents with:
- Jaundice (persistent conjugated hyperbilirubinemia).
- Pale stools and dark urine (reduced bile in stool).
- Hepatomegaly (due to inflammation and fibrosis).
- Elevated direct bilirubin and liver enzymes (ALT/AST).
- Hypoplastic or absent gallbladder on ultrasound.
Pathology:
Bile ductular proliferation occurs in response to biliary obstruction and is accompanied by portal tract fibrosis and eventual cirrhosis if untreated.
Incorrect answers:
B. Centrilobular necrosis: Seen in ischemic or toxic liver injury, not in biliary obstruction.
C. Increased glycogen stores: Associated with glycogen storage diseases, not biliary atresia.
D. Intranuclear hepatocytic inclusions: Seen in viral infections (e.g., CMV, HSV), not biliary atresia.
E. Macrovesicular steatosis: Seen in conditions like nonalcoholic fatty liver disease or metabolic disorders.
Question 29:
The correct answer is E. This 68-year-old man presents with acute-onset neurological symptoms, including ataxia, dysphagia, left-sided weakness, and right facial droop. These symptoms suggest a vascular event involving both motor pathways and cranial nerves. His ataxic gait and difficulty swallowing indicate brainstem involvement, while the combination of cranial nerve deficits (drooping on the right side of the face) and motor weakness (left-sided weakness) further localizes the lesion to the posterior circulation of the brain, supplied by the vertebrobasilar system.
The vertebrobasilar system includes the vertebral and basilar arteries, which supply the brainstem, cerebellum, thalamus, occipital lobe, and parts of the temporal lobe. Ischemia in this system can cause a constellation of symptoms depending on the specific vascular territory involved. The brainstem, where cranial nerve nuclei are located, is especially vulnerable. Classic findings of vertebrobasilar ischemia include dizziness, ataxia, dysphagia, and motor or sensory deficits that often cross hemispheres (e.g., ipsilateral cranial nerve findings with contralateral motor weakness, as seen here). This pattern is due to the involvement of both descending motor pathways and cranial nerve structures.
Incorrect answers:
A. Anterior cerebral artery supplies the medial frontal and parietal lobes. Infarction causes contralateral leg weakness and personality changes, not cranial nerve deficits or ataxia.
B. Internal carotid artery supplies both the anterior and middle cerebral arteries. Lesions here would result in a combination of middle and anterior cerebral artery symptoms, such as unilateral weakness and aphasia, not brainstem symptoms.
C. Middle cerebral artery supplies the lateral portions of the frontal, parietal, and temporal lobes. Infarction typically causes hemiparesis, hemisensory loss, and aphasia (if the dominant hemisphere is affected).
D. Posterior cerebral artery supplies the occipital lobe and inferior temporal lobe. Infarction results in visual field defects (e.g., homonymous hemianopia), not brainstem dysfunction.
A comprehensive guide to mastering the CCS part of the USMLE STEP 3 exam!

Question 30:
The correct answer is E. This 2-week-old newborn with trisomy 18 has significant congenital anomalies, including dysmorphic features, severe growth restriction (5th percentile weight and head circumference), and cardiac abnormalities. The prognosis is extremely poor, with most infants succumbing within the first month. Hospice care is appropriate to prioritize comfort and support for the family.
Trisomy 18 (Edwards syndrome):
Severe intellectual disability and congenital anomalies (e.g., heart defects, overlapping fingers, rocker bottom feet).
Median survival: Less than 2 weeks for neonates; <10% survive beyond the first year.
Hospice focuses on symptom management, quality of life, and family support.
Incorrect answers:
A. Admission to the hospital for a sleep apnea study: Sleep apnea evaluation is not appropriate in the context of severe, life-limiting congenital anomalies.
B. CT scan of the head: Unnecessary given the obvious clinical syndrome and poor prognosis.
C. Electroencephalography: Seizure assessment is not the priority here.
D. Referral to a cardiologist: Although the patient has a heart murmur, invasive interventions are unlikely to change outcomes.
Question 31:
The correct answer is D. This 58-year-old man presents with an acute inferior ST-elevation myocardial infarction (STEMI) involving leads II, III, and aVF, indicative of right coronary artery occlusion. His sudden hypotension after nitroglycerin administration strongly suggests right ventricular (RV) infarction. RV infarctions reduce preload as the RV maintains venous return. Nitroglycerin further decreases preload by causing venodilation, leading to severe hypotension in this setting.
RV infarctions are a subset of inferior STEMIs and are associated with occlusion of the right coronary artery. Clinical features include:
- Hypotension with clear lung fields (no pulmonary congestion).
- Jugular venous distension due to elevated central venous pressure.
- ST-segment elevation in the right-sided precordial leads (e.g., V4R).
Management focuses on maintaining RV preload. Volume resuscitation with intravenous fluids is critical to improve cardiac output, while preload-reducing agents like nitrates should be avoided. Reperfusion therapy with percutaneous coronary intervention (PCI) or thrombolysis is essential for restoring coronary blood flow.
Incorrect answers:
A. Acute mitral regurgitation: Results in pulmonary edema, a loud systolic murmur, and severe dyspnea, none of which are present here.
B. Pericardial tamponade: Causes hypotension, distant heart sounds, pulsus paradoxus, and jugular venous distension, absent in this case.
C. Pulmonary embolism: Typically presents with sudden dyspnea, hypoxemia, and pleuritic chest pain, not ST-segment elevation.
E. Vasovagal reaction: Causes bradycardia and hypotension without ST-segment changes or infarction.

Question 32:
The correct answer is D. The study shows that the intervention group experienced a reduction in the number of inflamed joints compared to the placebo group (7 vs. 2 joints, P = 0.02). The statistical significance (P < 0.05) indicates that the results are unlikely to have occurred by chance. Clinically, this 5-joint improvement is meaningful for patients with rheumatoid arthritis, as it suggests better symptom control and improved quality of life.
Statistical significance is determined by the P value, whereas clinical significance assesses whether the magnitude of the effect is meaningful to patients. Both aspects are important for interpreting the impact of a treatment.
Question 33:
The correct answer is B. This 60-year-old woman with a history of Parkinson disease, dementia, and bipolar disorder presents with confusion, falls, and an inability to recall her current medications. The patient is unable to provide accurate information about her medication regimen, and her primary support system (her brother) is unavailable. In this situation, contacting her pharmacy is the most practical and reliable approach to confirm her medication history, ensuring safe and appropriate care.
When managing a patient with cognitive impairment who cannot recall their medications, it is critical to obtain accurate information to prevent errors such as medication omissions or overdoses. Pharmacies maintain detailed records of dispensed medications, which can provide insight into the patient’s regimen, including recent changes or refills. This step minimizes the risk of adverse drug reactions, drug interactions, or complications from untreated conditions. Once the medication list is confirmed, the clinical team can evaluate whether her symptoms (e.g., falls, confusion) are related to medication side effects, withdrawal, or progression of her underlying conditions. In cases where the pharmacy records are insufficient or unavailable, additional measures like contacting her healthcare providers or family may be necessary.
Incorrect answers:
A. Ask the police to enter the brother’s house to locate the patient’s pill bottles: This is invasive and not immediately practical. Medication bottles at the house may not reflect the patient’s current regimen or dosing schedule.
C. Observe the patient closely while continuing to try to reach her brother: Observation delays definitive care and does not address the need to confirm the medication list. The brother is unavailable, making this approach inefficient.
D. Order the medications as listed in the emergency department record from her previous visit: Relying on outdated records is risky, as medication regimens may have changed since her last visit a year ago.
E. Order serum concentrations of the medications listed on the emergency department record: Measuring serum drug levels may help confirm adherence or toxicity but does not provide comprehensive information about her full medication regimen.
Question 34:
The correct answer is B. This question addresses a scenario where African American patients are underrepresented in a research study due to reluctance to enroll. Convening a representative focus group is an appropriate step to identify barriers and address concerns related to participation. This approach demonstrates respect for the community, ensures ethical research practices, and may improve enrollment by tailoring the process to address specific concerns.
Historically, distrust of the medical research system among minority groups has arisen from unethical practices.). Researchers must engage the community through culturally sensitive strategies, transparent communication, and measures to ensure ethical conduct.
Incorrect answers:
A. Ask the institutional review board to waive informed consent: This would violate ethical principles and further erode trust.
C. Focus recruitment efforts on White patients: This approach is discriminatory and fails to address the underrepresentation of minority groups.
D. Recognize this as unavoidable and continue as is: This response neglects the ethical obligation to address barriers and promote inclusivity.
E. Require all patients to participate: Mandatory participation violates autonomy and informed consent principles.
Question 35:
The correct answer is D. This 52-year-old man with cirrhosis presents with fever, hemorrhagic bullae, and hypotension, consistent with sepsis. His recent travel and exposure to warm seawater or ingestion of raw seafood suggest Vibrio vulnificus infection, a gram-negative bacterium commonly found in marine environments.
Vibrio vulnificus: Causes wound infections, sepsis, and bullous lesions, particularly in patients with liver disease (e.g., cirrhosis). Transmitted via contact with contaminated seawater or ingestion of raw shellfish.
Treatment: Immediate antibiotics (e.g., doxycycline + ceftriaxone). Supportive care for sepsis.
Incorrect answers:
A. Enterobacter aerogenes: Typically causes nosocomial infections, not associated with marine exposure.
B. Enterococcus faecalis: Commonly causes endocarditis or urinary infections, not associated with hemorrhagic bullae.
C. Mycobacterium marinum: Causes chronic granulomatous skin infections, not sepsis or bullous lesions.
Question 36:
The correct answer is B. This 55-year-old man with a fasting glucose of 126 mg/dL has impaired fasting glucose, placing him at risk for type 2 diabetes mellitus. Measurement of hemoglobin A1c is the most appropriate next step to confirm the diagnosis and assess long-term glucose control.
Diabetes Diagnosis (any one of the following):
- Fasting glucose ≥126 mg/dL.
- Hemoglobin A1c ≥6.5%.
- 2-hour glucose tolerance or random glucose ≥200 mg/dL
Incorrect answers:
A. Arterial blood gas values: Not indicated in a patient with no signs of acid-base disturbance or respiratory symptoms.
C. 3-hour glucose tolerance test: Used when initial tests are equivocal, but hemoglobin A1c is the preferred initial test.
D. Serum cortisol concentration: Unnecessary; there are no signs of adrenal insufficiency.
E. Serum fructosamine concentration: Reflects shorter-term glucose control (2–3 weeks) and is less commonly used than hemoglobin A1c.
Question 37:
The correct answer is D. This 3-month-old infant presents with respiratory distress characterized by head bobbing, nasal flaring, retractions, and wheezing. These symptoms are typical of bronchiolitis, a viral lower respiratory tract infection most commonly caused by RSV, particularly in children under two years old during winter. The chest X-ray findings of bilateral hyperinflation with peribronchial cuffing, combined with lymphocytosis (suggesting a viral etiology), and respiratory acidosis (low pH and elevated PCO2), further confirm the diagnosis.
RSV is the most frequent cause of bronchiolitis and pneumonia in young children. It primarily affects the small airways (bronchioles) by causing inflammation, edema, and increased mucus production, which lead to airway obstruction and impaired gas exchange. This results in wheezing, crackles, and hyperinflation, as seen on imaging. Infants with RSV bronchiolitis often develop respiratory failure due to increased work of breathing, leading to hypoxemia and hypercapnia. Management typically involves supportive care, including oxygen therapy and hydration. Routine use of bronchodilators or corticosteroids is not recommended unless there is a strong suspicion of an underlying reactive airway disease.
Differentiating RSV from bacterial or other viral infections is crucial:
Incorrect answers:
A. Haemophilus influenzae: is associated with bacterial epiglottitis or pneumonia, not diffuse bronchiolitis.
B. Herpes virus: Rarely causes bronchiolitis in infants and is associated with vesicular rashes or encephalitis, not respiratory distress.
C. Mycoplasma pneumoniae: is rare in infants and presents with patchy interstitial infiltrates in older children and adults.
E. Streptococcus pneumoniae: typically causes lobar pneumonia with focal consolidation and neutrophilic response.
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